Subsea Pipe Shearing Using Shape Charges
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Solution Overview
Problem
Blowout preventers struggle to effectively shear larger diameter and higher strength drill pipes, often due to insufficient accumulator pressure, which can lead to incomplete cutting and safety failures in emergency situations, especially when encountering materials like drill collars or other structures within the pipe.
Innovation Solution
The apparatus employs a housing with a shell containing shape charges directed at the pipe's outer diameter, actuated by a bladder inflated with hydraulic fluid from accumulator bottles, allowing for radial cutting of the pipe and any internal materials, providing redundancy to traditional shear rams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional shear rams are used to cut pipe, then the cutting mechanism is mechanically simple, but the cutting effectiveness deteriorates when pipe diameter, wall thickness, or yield strength increases
Solution Approach 1:
The patent replaces the traditional mechanical shear ram cutting system with an explosive-based shape charge system. The shape charge uses concentrated explosive energy to erode and sever the pipe, bypassing the limitations of mechanical cutting forces. This substitution enables reliable cutting of high-strength, thick-walled pipes that mechanical rams cannot effectively sever.
Solution Approach 2:
The invention changes the fundamental cutting parameter from mechanical force to explosive energy density. By using shaped charges with high explosive velocity and concentrated energy delivery, the system achieves cutting capability on high-strength materials without requiring proportionally higher mechanical forces, thus resolving the contradiction between mechanical simplicity and cutting effectiveness.
2Power
If accumulator pressure is increased to improve shearing capability, then cutting power increases, but the available pressure becomes insufficient for high-strength pipes
Solution Approach 1:
The patent replaces the hydraulic accumulator pressure system with an explosive-based energy delivery system. Shape charges store and release energy chemically rather than mechanically, providing vastly higher energy density and cutting power without requiring proportionally higher hydraulic pressures. This eliminates the pressure limitation while maintaining system feasibility.
Solution Approach 2:
The invention changes the energy delivery parameter from hydraulic pressure to explosive energy density. Shape charges provide concentrated energy release at the cutting interface, achieving high shearing power without the need for high accumulator pressures, thus resolving the contradiction between required power and available pressure.
3Adaptability or versatility
If blind shear rams are used to both shear pipe and seal wellbore, then the system achieves dual function in single movement, but reliability deteriorates when pipe cannot be fully sheared
Solution Approach 1:
The patent separates the cutting function from the sealing function. The shape charge system is dedicated solely to severing the pipe and any internal obstructions, while a separate sealing mechanism handles the wellbore closure. This segmentation ensures that the sealing action is not compromised by incomplete cutting, as the seal can close independently of cutting success.
Solution Approach 2:
The invention provides redundancy by ensuring the sealing function is independent and can compensate for cutting failures. The system is designed so that even if the shape charge does not fully sever the pipe, the sealing mechanism can still close the wellbore, providing a backup that cushions against the failure mode of incomplete cutting.
4Stress or pressure
If maximum anticipated pressure (15,000 p.s.i.) is achieved in the bore, then pressure protection is optimized, but the pressure acts against shear rams to restrict shearing ability
Solution Approach 1:
The patent replaces the mechanical shear ram system with an explosive shape charge system that is insensitive to bore pressure. The shape charge delivers cutting energy through explosive erosion rather than mechanical force, bypassing the adverse effect of high bore pressure opposing the cutting action. This substitution allows pressure protection to be maintained without compromising cutting capability.
Solution Approach 2:
The invention converts the harmful effect of high bore pressure opposing mechanical cutting into a non-issue by using explosive energy delivery. The shape charge's eroding jet cuts through the pipe regardless of the opposing pressure, effectively neutralizing the adverse effect and allowing both high pressure protection and effective cutting to coexist.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The shape charge system ensures effective cutting through pipes of any thickness and internal materials, ensuring safety by allowing the pipe to be completely severed and the well sealed, even when traditional shear rams fail, thus providing a reliable emergency shutdown mechanism.
Implementation Method 1
A shape charge is positioned in the shell and is directed toward an outer diameter of the pipe
Implementation Method 2
The bladder is inflatable so as to move an inner surface of the shell from the first position to the second position. An accumulator bottle is connected to the bladder so as to selectively introduce fluid into the bladder
Data Source
AI summary
An apparatus for the shearing of pipe in a subsea environment has a housing with an interior passageway suitable for allowing a pipe to extend therethrough, a shell positioned in the interior passageway of the housing, and a shape charge positioned in the shell so as to be directed toward an outer diameter of the pipe. The shaped charge includes a plurality of shape charges positioned in the shell so as to be directed to the outer diameter of the pipe. The plurality of shape charges extend radially within the shell. The plurality of shape charges are positioned in a common horizontal plane. The shell can be movable between a first position in which the shape charge is spaced from the pipe and a second position in which the shape charge bears against an outer diameter of the pipe.